The thermal nature of the Canadian Appalachian crust

Abstract Heat flow values for 17 new sites in the Canadian Appalachians of Nova Scotia, Prince Edward Island, New Brunswick and Quebec are reported. They consist of ten high-quality measurements obtained from a combination of accurate temperature gradient and thermal conductivity measurements, and seven values obtained from sites at which accurate temperature data were obtained but at which lack of core material meant that conductivity had to be estimated from lithological information. The mean and standard deviation of heat flow from the new sites is 58 ± 11 mW/m 2 , not significantly different from the mean and standard deviation obtained by incorporating seventeen previously published values, 57 ± 11 mW/m 2 . Heat flow varies across this part of the Canadian Appalachians, being lowest in the central part, which is underlain by a major Carboniferous basin, and highest near the coast. There is no obvious relationship between heat flow and age of orogenic imprint. In southern New Brunswick there is an area of high heat flow, greater than 70 mW/m 2 , that appears to be related to the presence of radiogenic Devonian granitic batholiths, both exposed and buried. Using a previously defined heat flow-heat generation relationship for the Appalachians of Canada, the radiogenic layer is estimated to be approximately 1.4 to 3.3 km thick in the St. George batholith of New Brunswick, and surficial in the Wedgeport pluton of Nova Scotia. Gravity interpretation suggests that the maximum thickness of the St. George batholith is 7.5 km. Very low values of heat flow are reported for the Magdalen Basin. Up to 10 km of crust may have been eroded from the basement prior to the formation of the southern part of the basin, removing much of the radiogenic source of heat.